Circuit connecting means of the plug in type



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CIRCUIT CONNECTING MEANS OF' THE PLUG IN TYPE 2 Sheets-Sheet 1 Filed March 19, 1965 .Uf los E. BoRYs 3,313,960

CIRCUIT CONNECTING MEANS OF THE PLUG 1N TYPE April 11, 1967 2 Sheets-Sheet 2 Filed March 19, 1965 mwN United States Patent O 3,313,960 CIRCUIT CONNECTlNG MEANS OF THE PLUG IN TYPE Emil Borys, 710 Old Rand Road, Lake Zurich, Ill. 60047 Filed Mar. 19, 1963, Ser. No. 266,385 4, Claims. (Cl. 307-127) This invention relates, generally, to circuit connecting means and it has particular relation to plug-in connecting means employed for energizing a load device from a two conductor alternatin-g current energizing circuit, one conductor of which is grounded.

In order to reduce to a minimum the likelihood of a person accidentally coming in contact with the ungrounded conductor of a pair of conductors energized from a conventional 115 volt alternating current source, it is desirable that provision be made for insuring that the terminal of a load device intended for connection to such ungrounded conductor be connected to the same and not to the grounded conductor. While this can be accomplished by ernploying a plug and socket arrangement which can be cornpleted in only one rather than two ways or is polarized, such an arrangement is not presently conventional and the majority of sockets and plugs employed for energizing such devices as household appliances, motor driven tools, coin controlled electrically operated device and the like are unpolarized with the result that, when a plug is inserted in a convention-al socket, one terminal or side of which is or should `be grounded, the chances are equal as to whether the plug will be or will not be inserted in such relation that the conductor connected thereto and intended to be grounded will in fact be connected to the grounded side of the socket.

Accordingly, among the objects of this invention are: To provide for insuring that the prongs of a plug employed for energizing a load device of the kind and character above mentioned over a two conductor circuit cannot be inserted in a socket energized from a conventional two conductor alternating current source one conductor of which is grounded in such manner that the two conductor circuit to the load device can be energized except when the plug is inserted in only one of the two possible positions; to connect a load device for energization to an alternating current source one terminal of which is grounded in such manner that the load device cannot be energized unless a predetermined circuit connection is made; to interconnect a two conductor cable connected to a load device and a plug for insertion in a socket energized from a two conductor alternating current source with one conductor grounded in such manner that the circuit cannot be completed unless a predetermined relation exists with respect to the position of the plug in the socket; to employ a relay for this purpose and to energize it to close contacts for completing the circuit only when the plug is properly inserted in lthe socket; to energize the relay as the result of manual completion of a circuit than can be effected only when the plug is properly inserted in the socket; to cause the emission of light on proper insertion of the plu-g; to employ the light thus emitted for effecting the energization of the relay; to open the circuit completed on application of light when the relay is energized; and to provide a circuit for maintaining the relay energized as long as the plug remains in the socket and the socket is energized from the alternating current source.

In the drawing FIG. l illustrates a `diagrammatically a preferred circuit arrangement embodying the present invention.

FIG. 2 illustrates a modification.

Referring now to FIG. 1 of the drawing, it will be observed that the reference character designates, generally, a load device which may have a metallic housing 11 and an energizable element 12 therein. It will be understood that the energizable element 12 may comprise the winding of a motor, a heating element of a heater or like device. In general, as pointed out above, the load device 10 may comprise a household appliance such as a refrigerator or Washing machine and the like or it may comprise a coin operated electrically operated device such as an automatic record player or like device. Ordinarily, the metallic housing 11 is grounded and it is desirable that the energizing conductors for the element 12 be properly connected for energization to a source even though they are normally insulated from the metallic housing 11.

A conventional two conductor energizing circuit is indicated at 13. It comprises conductors 14 and 15 that are energized at a conventional voltage of the order of volts from a suitable alternating current source operating at a frequency of 60 cycles per second or some other frequency. The conductors 14 and 15 are connected, in conventional manner, to energize socket members 16 and 17 of a socket that is indicated, generally, at 18. This may be a conventional wall socket in which the socket mem- 'ber 17 and conductor 15 connected thereto are grounded as indicated at 19.

The socket 18 is arranged to receive plug prongs 20 and 21 that extend from a plug that is indicated, generally, at 22. Since the plug prongs 20 and 21 are conventionally of symmetrical construction, the plug 22 can be inserted in the socket 18 in either of two ways so that either the prong 20 or the prong 21 may be connected to ground 19. In accordance with the present invention provision is made for preventing the energization of the load device 10 except when the plug 22 is inserted in the socket 18 in such manner that the prong 21 is connected to ground 19 while the prong 20 is connected to the ungrounded conductor 14.

The circuit extends from the plug 22 through conductors 24 and 25 that are embedded in suitable insulation and comprise a two conductor cable which extends from the load device 10 Where the conductors 24 and 25 are connected to the terminals of the energizable element 12, to an insulating housing 26 which forms a part of the plug 22. The arrangement is such that, in order to energize the load device 10, it is necessary that the plug 22 with associated housing 26 be inserted in the socket 18.

The insulating housing 26 is arranged to be grasped in the hand of an operator for inserting the plug 22 into the socket 18. When this action takes place the operators hand comes in contact with a metallic grounding band 27 that surrounds the housing 26. The band 27 can be in the form of a metallic ring or it can be provided by a number of turns of wire, such as copper wire, as may be desired. Its purpose will be set forth presently.

Mounted wit-hin the housing 26 is a relay that is indicated, generally, at 28. The relay includes normally open contacts 28a which, when closed, serve to complete the circuit from the prong 21 through the conductor 25 to the load device 10. As long as the operating winding 28W of the relay 28 is not energized, these contacts 28a are open and the circuit cannot be completed. The relay 28 also is provided with an addition-al set of normally open contacts 28h and a set of normally closed contacts 28C lthe function of which will be described presently.

With a view to providing means responsive to the contact of the hand of the operator with the metallic grounding band 27, a glow discharge device 29 is employed. It may be a neon bulb and it is connected through a resistor 30 to that portion of the conductor 24 which is connected directly to the prong 20. The glow discharge device 29 is also connected at 32 to the grounding band 27. The capacitance of the body of the operator is indicated at 33 and ground is indicated at 34. Now, it will be apparent when the plug 22 is inserted in the socket 18 with the prong 26 in engagement with the socket member 16, a circuit will be completed through the body of the operator which, while of relatively high resistance and in capable of being sensed by the operator, nevertheless it is suicient to energize the glow discharge device 29 and cause it to emit light.

Associated with the glow discharge device 29 is a light sensitive device 35 in the form e a photoelectric cell having an anode 35a and a cathode 35C. When the light is emitted from the glow discharge device 29 and impinges on the cathode 35C, the resistance of the light sensitive device 35 is greatly reduced. The light sensitive device 35 is connected to control the operation of a circuit which includes a transistor or other similar triggerable device that is indicated, generally, at 36. If a transistor, it has a base 36h which is connected to the cathode 35e of the light sensitive device 35. In addition the transistor 36 includes an emitter 36e which is biased from rectifier 37 that is connected through a resistor 39 and between the conductors 24 and 25 for energization. A capacitor 4t), connected across the rectifiers 37 and 38, serves to take out the ripple of the alternating current. The collector 36e of the transistor 36 is connected in series with the operating winding 28W of the relay 28 for the purpose of effecting energization thereof when the conductivity of the transistor 36 is changed by the application of light to the light sensitive device 35. A resistor 41 interconnects the base 3611 and the emitter 36e.

Since the energization of the glow discharge device 29 in the manner described ordinarily will be of momentary duration, it is desirable that the operating winding 28W remain energized. For this purpose the additional set of normally open contacts 2gb is provided. They are connected in such fashion that a resistor 42 acts as a shunt across light sensitive device 35 after coil 28w is energized.

Now assuming that the load device is to be energized, the plug 22 is inserted in the socket 18 in the relationship indicated in the drawing. Also it will be assumed that the operator engages the metallic grounding band 27. As soon as the prongs 2t) and 21 are in contact engagement with the socket members 16 and 17, the glow discharge device 29 is energized and light emitted therefrom impinges on the cathode 35C of the light sensitive device 35. Thereupon the transistor 36 is caused to conduct suficient current through the operating winding 29W to effect its energization and close contacts 28a.

This completes the circuit through the conductor 25 to the load device 10 and it is energized. At the same time contacts 28e are opened to open the circuit to the light sensitive device 35 and thereafter contacts 2817 are closed to complete a biasing holding circuit through the resistor 42 for the transistor 36. As a result the operating Winding 28W continues to be energized as long as the conductors 14 and 15 are energized in the manner described. When the plug 22 is withdrawn from the socket 18 or when then the conductors 14 and 15 are deenergized, the energizing circuit for the operating winding 28W is no longer maintained. Contacts 28a and 28h are opened and contacts 28e are closed. Thereafter the cycle of operation can be repeated.

Should the plug 22 be inserted in the socket 18 in reverse position with the prong 20 in engagement with the grounded socket member 17, it is not possible to energize the glow discharge device 29. Accordingly, since no light is emitted therefrom under these conditions, the light sensitive device 35 does not have its resistance reduced. No action takes place and the load device 10 cannot be energized. 1t then becomes apparent to the operator that the position of the plug 22 must be reversed in order to effect energization of the load device 10.

Referring now to FIG. 2 of the drawings, it will be observed that the reference character 50 designates, generally, a load device which may have a metallic housing 51 and an energizable element 52 therein. It will be understood that the energizable element 52 may comprise the winding of a motor, a heating element of a heater or like device. In general, as pointed out above, the load device Si) may comprise a household appliance such as a refrigerator or washing machine and the like or it may comprise a coin operated electrically operated device such as an automatic record player or like device, electrically operated power tools, or floor lamps, table lamps, or kitchen appliances such as toasters, electric beaters and like devices. Ordinarily, the metallic housing 51 is grounded and it is desirable that the energizing conductors for the element 52 be properly connected for energization to a source even though they are normally insulated from the metallic housing 51.

A conventional two conductor energizing circuit is indicated at 53. It comprises conductors 54 and 55 that are energized at a conventional voltage of the order of 115 volts from a suitable alternating current source operating at a frequency of 60 cycles per second or some other frequency. The conductors 54 and 55 are connected, in conventional manner, to energize socket members 56 and 57 of a socket that is indicated, generally, at 58. This may be a conventional wall socket in which the socket member 57 and conductor 55 connected thereto are grounded as indicated at 59.

The socket 58 is arranged to receive plug prongs 60 and 61 that extend from a plug that is indicated, generally, at 62. Since the plug prongs 60 and 61 are conventionally of symmetrical construction, the plug 62 can be inserted in the socket 58 in either of two ways so that either the prong 60 or the prong 61 may be connected to ground 59. In accordance with the present invention, provision is made for preventing the energization of the load device 50 except when the plug 62 is inserted in the socket 58 in such manner that the prong 60 is connected to ground 59 while the prong 61 is connected to the ungrounded conductor 54.

The circuit extends from the plug 62 through conductors 64 and 65 that are embedded in suitable insulation and comprise a two conductor cable which extends from the load device 50 where the conductors 64 and 65 are connected to the terminals of the energizable element 52, to an insulating housing 66 which forms a part of the plug 62. The arrangement is such that, in order to energize the load device 50, it is necessary that the plug 62 with associated housing 66 be inserted in the socket 58.

The insulating housing 66 is arranged to be grasped in the hand of an operator for inserting the plug 62 in the socket 58. When this action takes place the operators hand comes in contact with a metallic grounding band 67 that surrounds the housing 66. The band 67 can be in the form of a metallic ring or it can be provided by a number of turns of wire, such as copper wire, as may be desired. Its purpose will be set forth presently.

Mounted within the housing 66 is a relay that is indicated, generally, at 68. This relay includes normally open contacts 68a which, when closed, serve to complete the circuit from the prong 60 through the conductor 64 to the load device 50. As long as the operating winding 68W of the relay 68 is not energized, these contacts 68a are open and the circuit cannot be completed. The relay 68 is also provided with an additional S.P.D.T. switch, generally, at 68s and a set of normally closed contacts at 68C, the function of which will be described presently.

With a view to providing means responsive to the contact of the hand of the operator with the metallic grounding band 67, a glow discharge device 69 is employed. It may be a neon bulb and it is connected through resistor 70, diode 70a, and normally closed contacts 68C, to that portion of conductor which is connected directly to prong 61. The glow discharge device 69 is connected at 72a to the base 76b of a transistor 76, to R1 reverse bias resistor, and at 72 to grounding band 67. Resistor acts as a current limiting device. Diode 70a is used to prevent a current flow across R2 between diode 77 and conductor 65. At 72b, the glow discharge device is connected to R2 forward bias resistor, of the transistorized relay circuit. The capacitance of the body of the operator is indicated at 73 and ground i-s indicated at 74. Now it will be apparent that when plug 62 is inserted in socket 58 with prong 61 in engagement with socket member 56, a circuit will be completed through the body of the operator which, while of relatively high resistance, and incapable of being sensed by the operator, nevertheless it is sufiicient to energize the glow discharge device 69, causing it to emit light, and pass a minute amount of current.

Associated with the glow discharge circuit, is the forward bias portion of the transistor circuit. When the glow discharge device circuit is completed and is passing current, the glo-w discharge device acts as a closed switch within the transistor circuit, allowing current to flow through the operating winding 68W for the purpose of effecting energization thereof. The transistor has a base 76b which is biased through glow device 69, which said glow device 69 acts as a normally open switch until energized, through resisto-r R2 to the negative side of the power supply composed of rectifiers 77 and 78, capacitor 80, resistor 83, through resistor 79. The collector 76C is connected in series with the operating winding 68W of the relay 68 for the purpose of effecting energization thereof when the conductivity of the transistor 76 is changed by the closing `of the negative bias to base 76b circuit through energizing glow device 69. A resistor R1 interconnects the base 76b and emitter 76e. Since the energization of the glow discharge device 69 in the manner described ordinarily will be of momentary duration, it is desirable that the operating winding 68W remain energized. For this purpose the additional S.P.D.T. switch 68s is provided. Normally closed contacts 68C are provided to cut glow device 69 out of circuit upon energization of coil 68W. Now, assuming that the plug 62 is inserted in the socket 58 in the relationship indicated in the drawing, it is not possible to energize the glow discharge device 69, the negative bias section of the transistorized circuit is open, therefore operating winding 65W cannot be energized. With no action taking place, load device 50 cannot be energized. It then becomes apparent to the operator that the position of the plug 62 must be reversed in order to effect energization of the load device 50'.

With plug 62 inserted in the socket 58 in the reverse of the relationship as indicated in the drawing and assuming that the yoperator engages the metallic grounding band 67, as soon as the prongs 60 and 61 are in contact engagement with the socket members 57 and 56 respectively, the glow discharge device 69 is energized, causing circuit to be closed between resistor R2 and base 76b. Thereupon the transistor 76 is caused to conduct sufficient current through the operating winding 69W to effect its energization and close contacts 68a. rl'ihis comipletes the circuit through the conductor 64 to the load device 50 and it is energized. At the same time contacts 68e are opened to open the circuit to the glow device 69. Also, at the same time, switch 68s opens the circuit between collector 76c and operating winding 68W and effects an independent holding circuit for operating winding 68W. As a result, the operating winding 68'w continues to be energized so long as the conductors '54 and 55 are energized in the manner described. When plug 62 is withdrawn from the socket 58 or when then the conductors 54 and 55 are deenergized, the energizing circuit for the operating winding 68W is no longer maintained. Contacts 68C and 68u are opened and closed, contact switch 68s returns to its original position, and thereafter the cycle of operation can be repeated.

If a silicon controlled rectifier is used in place of the transistor, the circuit is similar with the cathode corresponding to the emitter, the anode corresponding to the collector and the base corresponding to the gate.

What is claimed as new is:

t1. Means for interconnecting a load device and a two conductor alternating current energizing source having one conductor grounded comprising:

(a) a relay having an energizing winding and normally open contacts for completing when closed a circuit between the ungrounded conductor of said two conductors and said load device,

(tb) light emitting means adapted to be connected for energization between said ungrounded conductor and ground,

(c) a light sensitive device disposed to have its conductivity changed when light from said light ernitting means impiirges thereon and connected to effect energization of said winding and closure of said contacts only when said circuit is connected to said ungrounded cond-uctor,

(d) an insulating housing enclosing said relay, light emitting means and light sensitive device,

(e) a two prong plug on said housing for insertion into a socket to which said two conductor alternating current energizing source is connected with one prong being connected to said circuit completed by said contacts and the other prong ybeing connected to a conductor extending through said housing for connection to said load device,

(f) a two conductor cable extending from said housing with the conductors therein for connection to said load device at one end and at the other end for connection to the portion of said circuit completed by closure of said contacts and to said conductor extending through said housing respectively, and

(-g) metallic means ou said housing connected to said light emitting means and adapted to be grasped manually whereupon a circuit to ground is completed for said light emitting means.

t2. The invention, as set forth in claim 1, wherein means are provided for opening the energizing circuit for the light sensitive device on energization of the relay winding and for maintaining the latter energized as long as the circuit remains energized from the two conductor alternating current source.

3. vMeans for interconnecting a load device and a two conductor alternating current energizing source having one conductor grounded comprising:

(a) a relay having an energizing winding and normally open contacts for completing when closed a circuit ,between the ungrounded conductor of said two conductors and said load device,

(b) a circuit sensing device adapted to be connected for energization lbetween said ungrounded conductor and ground,

(c) a device disposed to act as a closed switch upon energization and Aconnected to effect energization of said Iwinding and closure of said contacts only when said circuit is connected to said ungrounded conductor,

(d) an insulating housing enclosing said relay, circuit sensing device, and switch device and having a two prong plug for insertion into a socket to which said ftwo conductor alternating current energizing source is connected with one of said prongs connected to said circuit completed by said contacts and the other prong connected to a conductor extending through said housing for connection to said load device,

(e) a two conductor cable extending from said housing 'with the conductors therein for connection to said -load device at one end and at the other end for connection to the portion of said circuit completed 'by closure of said contacts and to the conductor extending through said housing respectively, and

(f) metallic means on said housing connected to said circuit sensing device and adapted to be grasped manually whereupon a circuit to ground is completed for said circuit sensing means.

4. The invention, as set forth in claim 3, wherein means are provided for opening the energizing circuit for the circuit sensing device on energization of the operating winding and for maintaining the latter ener- .gized as long as the circuit remains energized from the two conductor alternating current source.

References Cited by the Examiner UNITED STATES PATENTS tag Company.

FOREIGN PATENTS 5/1964 Canada.

OTHER REFERENCES Electronics at Work in the Home, Maytag Electronic Dryers Service Department, Copyright 1960, The May- ORIS L. RADER, Prima/'y Examiner.

L. MCCOLLUM, Examiner.

T. I. MADJDEN, W. SHOOP, Asssm/l! Examiners. 

1. MEANS FOR INTERCONNECTING A LOAD DEVICE AND A TWO CONDUCTOR ALTERNATING CURRENT ENERGIZING SOURCE HAVING ONE CONDUCTOR GROUNDED COMPRISING: (A) A RELAY HAVING AN ENERGIZING WINDING AND NORMALLY OPEN CONTACTS FOR COMPLETING WHEN CLOSED A CIRCUIT BETWEEN THE UNGROUNDED CONDUCTOR OF SAID TWO CONDUCTORS AND SAID LOAD DEVICE, (B) LIGHT EMITTING MEANS ADAPTED TO BE CONNECTED BY ENERGIZATION BETWEEN SAID UNGROUNDED CONDUCTOR AND GROUND, (C) A LIGHT SENSITIVE DEVICE DISPOSED TO HAVE ITS CONDUCTIVITY CHANGED WHEN LIGHT FROM SAID LIGHT EMITTING MEANS IMPINGES THEREON AND CONNECTED TO EFFECT ENERGIZATION OF SAID WINDING AND CLOSURE OF SAID CONTACTS ONLY WHEN SAID CIRCUIT IS CONNECTED TO SAID UNGROUNDED CONDUCTOR, (D) AN INSULATING HOUSING ENCLOSING SAID RELAY, LIGHT EMITTING MEANS AND LIGHT SENSITIVE DEVICE, (E) A TWO PRONG PLUG ON SAID HOUSING FOR INSERTION INTO A SOCKET TO WHICH SAID TWO CONDUCTOR ALTERNATING CURRENT ENERGIZING SOURCE IS CONNECTED WITH ONE PRONG BEING CONNECTED TO SAID CIRCUIT COMPLETED BY SAID CONTACTS AND THE OTHER PRONG BEING CONNECTED TO A CONDUCTOR EXTENDING THROUGH SAID HOUSING FOR CONNECTION TO SAID LOAD DEVICE, (F) A TWO CONDUCTOR CABLE EXTENDING FROM SAID HOUSING WITH THE CONDUCTORS THEREIN FOR CONNECTION TO SAID LOAD DEVICE AT ONE END AND AT THE OTHER END FOR CONNECTION TO THE PORTION OF SAID CIRCUIT COMPLETED BY CLOSURE OF SAID CONTACTS AND TO SAID CONDUCTOR EXTENDING THROUGH SAID HOUSING RESPECTIVELY, AND (G) METALLIC MEANS ON SAID HOUSING CONNECTED TO SAID LIGHT EMITTING MEANS AND ADAPTED TO BE GRASPED MANUALLY WHEREUPON A CIRCUIT TO GROUND IS COMPLETED FOR SAID LIGHT EMITTING MEANS. 